The present invention relates to a vehicle occupant protection device. In particular, the present invention relates to a method and apparatus using a weight based occupant classification system for controlling the enabling and disabling of actuation of a protection device for an occupant of a vehicle seat.
It is known to disable a vehicle occupant protection device, such as an air bag for an occupant of a vehicle seat, if it is determined that the occupant of the seat is under a certain weight. Various methods have been proposed for determining the occupant weight, typically involving the use of weight sensors in the seat. With a weight sensor, it may be important to distinguish between the weight of an adult seated in the seat, of a child seated in a child seat, of a child seat cinched down tight in the vehicle seat, and of an adult in the process of cinching the child seat down.
The typical weight threshold for distinguishing between a child and an adult is the 60-70 pound range of seated weight, that is, the sensed weight on the seat bottom cushion, not including any weight that may be transferred to the floor through the legs of an occupant. One-time sensing of seated weight in excess of this threshold, by itself, may not always be sufficient to discriminate properly between a child and an adult. For example, a six year old child, weighing in the range of 50 pounds, can be seated on a child seat weighing up to 20 pounds, for a total seated weight in the range of 70 pounds. Cinching the child seat down on the vehicle seat, with the seat belt, can increase the seated weight to an amount in the range of 70 pounds to 80 pounds. This is a seated weight that is in the range of the seated weight of some adults, for example, a small female with a total body weight of 108 pounds where a portion of the weight, up to 30 pounds or more, rests on the floor. In this child seat case, actuation of an air bag inflator might be enabled when it should preferably be disabled.
As another example, an adult may kneel on a child seat to cinch the child seat down with a seat belt, temporarily increasing the seated weight to a weight in the range of 100 pounds or more. Again, in this case, actuation of the air bag system might be enabled when it should preferably be disabled.
The present invention is a method of controlling enabling and disabling of actuation of a protection device for an occupant of a vehicle seat having a weight sensor. The method comprises the steps of:
continually sensing the weight on the vehicle seat and providing an output signal indicative of the sensed weight;
determining when the value of the output signal of the weight sensor rises from an initial value;
waiting a predetermined period of time after the value of the output signal rises from the initial value;
determining the weight on the vehicle seat after the predetermined period of time;
comparing the weight on the vehicle seat after the predetermined period of time with a first threshold weight;
enabling actuation of the protection device if the weight on the vehicle seat after the predetermined period of time exceeds the first threshold weight; and
disabling actuation of the protection device if the weight on the vehicle seat after the predetermined period of time does not exceed the first threshold weight.
The present invention is also an apparatus for controlling enabling and disabling of actuation of a protection device for an occupant of a vehicle seat having a weight sensor. The apparatus comprises a sensor for sensing the weight on the vehicle seat and for providing an output signal indicative of the sensed weight. The output signal has an initial value. The apparatus also comprises means for determining when the value of the output signal rises from the initial value, and means for determining the weight on the vehicle seat at a predetermined period of time after the value of the output signal rises from the initial value. The apparatus further comprises means for comparing the weight on the vehicle seat after the predetermined period of time with a first threshold weight. The comparing means enables actuation of the protection device if the weight on the vehicle seat after the predetermined period of time exceeds the first threshold weight. The comparing means disables actuation of the protection device if the weight on the vehicle seat after the predetermined period of time does not exceed the first threshold weight.